Field of the Invention
The present invention generally relates to image forming apparatus, such as copying machines, facsimile machines, printers and copying/facsimile/printing machines, and more particularly, to a device for preventing a fixing unit, provided within the image forming apparatus to fix a toner image transferred on a sheet onto the sheet, from inadvertently falling off of the apparatus.
Discussion of the Background
FIG. 1 is a schematic drawing illustrating a construction of a conventional printer for explaining a method of removing a fixing unit from a main body of the printer. Reference numeral 1 denotes the main body of the printer, reference numeral 2 denotes a sheet cassette, and reference numeral 3 denotes an electrophotographic image forming unit, which includes a photoconductor 4. Reference numeral 5 denotes the fixing unit, which includes a heating roller 6 and a pressing roller 7. The fixing unit 5 fixes a toner image, which has been transferred by the electrophotographic image forming unit 3 onto a recording sheet P by applying heat and pressure. Reference numeral 8 denotes a conveying path for the recording sheet P and reference numeral 9 denotes a discharging roller for discharging the recording sheet P after a fixing operation has been accomplished thereon to a discharged sheet tray 10. Reference numeral 111 denotes an openable and closable cover that opens and closes to uncover and cover, respectively, a front side of the conveying path 8 and the fixing unit 5 (the right side in FIG. 1).
The fixing unit 5 is detachably provided inside of the main body 1 of the printer so that the fixing unit 5 can be detached from the main body 1, for example, for replacement with a new one. At an upper front part of the fixing unit 5, a fixing unit supporting lever 12 and a pressure releasing lever 13 are provided side by side. The fixing unit supporting lever 12 is depressed to release a support of the fixing unit 5 in the main body 1 when removing the fixing unit 5 from the main body 1 for replacement, for example, and the pressure releasing lever 13 is depressed to release an applying pressure of the pressing roller 7 when removing a recording sheet P which has become jammed at a nip between the heating roller 6 and the pressing roller 7.
The cover 11 is supported by an axis 14 at a bottom part of the cover 11 so as to be rotatable relative to the main body 1. The cover 11 is opened to uncover the inside of the main body 1 when replacing the fixing unit 5 or when removing a recording sheet P which has become jammed at the conveying path 8 or in the fixing unit 5. Under normal conditions, the cover 11 is closed to cover the fixing unit supporting lever 12 and the pressure releasing lever 13, and the front side of the conveying path 8 and the fixing unit 5 as well.
When replacing the fixing unit 5, the user first opens the cover 11 to uncover the front side of the main body 1, depresses the fixing unit supporting lever 12, and then draws out the fixing unit 5. When removing a recording sheet P which has become jammed at the nip between the heating roller 6 and the pressing roller 7 of the fixing unit 5, the user likewise opens the cover 11 to uncover the front side of the main body 1, and then depresses the pressure releasing lever 13 to release the pressure of the pressing roller 7 for facilitating the clearance of the jammed recording sheet P.
However, in the above-described conventional printer, the fixing unit supporting lever 12, which is used when replacing the fixing unit 5, and the pressure releasing lever 13, which is used when removing a jammed recording sheet P at the nip between the heating roller 6 and the pressing roller 7, are arranged in close proximity to each other. Further, both the fixing unit supporting lever 12 and the pressure releasing lever 13 are operated by depressing operations which closely resemble each other. Therefore, the user tends to erroneously operate the fixing unit supporting lever 12, not the pressure releasing lever 13, for removing a jammed recording sheet P. Further, the user often inadvertently touches the fixing unit supporting lever 12 while operating the pressure releasing lever 13.